1. Field of the Invention
The present invention relates to clamp technology, and more particularly to an F type clamp that provides a locking function.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional F type clamp 1 generally comprises a rail 2, a locating frame bar 3 extended from one end of the rail 2 at right angles, a sliding bar 4 having a through hole 5 located at one end thereof and slidably coupled to the rail 2, a screw rod 6 threaded through an opposite end of the sliding bar 4, a handle 7 fixedly connected to one end of the screw rod 6, and a jaw plate 8 fixedly located at an opposite end of the screw rod 6 for working with the locating frame bar 3 to hold down a workpiece. Further, the through hole 5 tilts relative to the rail 2, defining an upper bearing point A and a lower bearing point B. Under normal conditions, the upper bearing point A and the lower bearing point B are respectively abutted against two opposite sides of the rail 2, securing the sliding bar 4 to the rail 2 in position and giving a pressure to the screw rod 6 to force the jaw plate 8 against the workpiece and the locating frame bar 3.
According to the aforesaid prior art F type clamp 1, when going to adjust the position of the sliding bar 4 relative to the rail 2, the user needs to bias the sliding bar 4 to further move the through hole 5 to a parallel manner relative to the rail 2, disengaging the upper bearing point A and the lower bearing point B from the rail 2 and allowing the sliding bar 4 to be moved freely along the rail 2. However, when the applied pressure is disappeared after the adjustment, the effect of the gravity weight of the sliding bar 4 and the screw rod 6 can cause displacement of the sliding rail 4 relative to the rail 2 for a certain distance, affecting the accuracy of the positioning of the sliding bar 4 on the rail 2. Further, if the user's hand touches the bottom side of the sliding bar 4, the sliding bar 4 can be vibrated accidentally, causing transient disengagement of the upper bearing point A and the lower bearing point B from the rail 2 and leading to downward sliding movement of the sliding bar 4 relative to the rail 2 or accidental injury. Further, accidental vibration of the F type clamp 1 or the worktable can cause transient disengagement of the upper bearing point A and the lower bearing point B from the rail 2 and displacement of the sliding bar 4 relative to the rail 2, leading to workpiece clamping failure. Improvement in this regard is necessary.